Yamaha MBK MW125 2014, Service Manual

Page: 257 / 380

ELECTRIC STARTER
5-54
EAS30325
CHECKING THE STARTER MOTOR
1. Check:
• Commutator
Dirt
→
Clean with 600 grit sandpaper.
2. Measure:
• Commutator diameter “a”
Out of specification
→
Replace the starter
motor.
3. Measure:
• Mica undercut “a”
Out of specification
→
Scrape the mica to the
proper measurement with a hacksaw blade
that has been grounded to fit the commutator.
TIP
The mica of the commutator must be undercut to
ensure proper operation of the commutator.
4. Measure:
• Armature assembly resistances (commutator
and insulation)
Out of specification
→
Replace the starter
motor.
▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼ ▼▼▼ ▼ ▼▼▼
a. Measure the armature assembly resistances
with the digital circuit tester.
b. If any resistance is out of specification, re-
place the starter motor.
▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲ ▲▲▲ ▲ ▲▲▲
5. Measure:
• Brush length “a”
Out of specification
→
Replace the brushes
as a set.
6. Measure:
• Brush spring force
Out of specification
→
Replace the brush
springs as a set.
Commutator diameter
22.0 mm (0.87 in)
Limit
21.0 mm (0.83 in)
Mica undercut (depth)
1.50 mm (0.06 in)
a
Digital circuit tester
90890-03174
Model 88 Multimeter with ta-
chometer
YU-A1927
Armature coil resistance
0.0315–0.0385
Ω
Insulation resistance “2”
No continuity (Above 1 M
Ω
at 20
°C (68 °F))
Brush overall length
9.5 mm (0.37 in)
Limit
3.50 mm (0.14 in)
1
2
a